Depends on what you are doing with it and how it's geared. To keep a really long post shorter:
I've put my CK through a lot of every use now and all 3 of the speed ranges are necessary to get the full work out of the tractor.
Low and 4wd is all but required when scooping big buckets of dirt from an old pile. Also for ground engagement with the box blade. And for moving our larger trailers.
Medium does all normal weight work and gets you from A to B in good time. Forking, grappling, repositioning, light towing, general movement. Whatever.
High is the only one I'd consider sort of expendable, but when I have to cross the entire property or go a quarter mile down the road... it saves a ton of time. I find myself using it more than expected. And yes it hates going up steep hills in this gear, that's not what it's for.
As for size... I move small trees and big ones cut into 8ft sections frequently. Wouldn't want anything smaller for that job that's for sure.
